A conventional endoscopic apparatus for measuring the size of a diseased portion within a human's body is disclosed in Gastroenterological Endoscopy, Vol. (25) 6, p. 868, published in June 1983 where two-dimensional diffracted spot light provided when laser beam is diffracted by a fiber diffraction grating of a penetrating type is projected onto an inspected object to obtain predetermined information with respect to the measurement.
In this conventional example, a predetermined clearance is disposed between an arranged place of the fiber diffraction grating at an end of a scope, and an observing point where an objective lens, an image pick-up element, etc., are disposed. When the two-dimensional diffracted spot light diffracted by the fiber diffraction grating is projected on the inspected object and a projected image is observed from the observing point, a change corresponding to the shape of the inspected object is generated in the clearance between the spot light projected onto the inspected object. The distance between the observing point and the inspected object such as a diseased portion, and the size thereof are measured to obtain information about the situation and extension of irregularity of the diseased portion.
However, in this conventional example, the irregularity of the diseased portion is not exactly measured three-dimensionally, and cannot be displayed on a monitor, etc., at real time.
A second conventional example is disclosed in "restoration of the shape and position information of a three-dimensional object by an illuminance difference stereo-method" of Vol. J69-D, No. 3. pp 427-433, written by Ko, Kawashima, and Aoki published by Singakuron on March, 1986. In this method, the shape of the three-dimensional object can be restored by using a difference in illumination intensity.
However, in this second conventional example, the distance is treated as a known parameter, and only a principle of the restoration technique is disclosed, thereby providing no solution with respect to a detailed technique for applying to an endoscope the measurement of irregularity of a diseased portion with a human's body.